Dental cements are usually powder liquid systems consisting of linear poly(alkenoic acid)s and reactive ion releasing active glasses. The most common poly(alkenoic acid)s are polymers such as polyacrylic acid or copolymers of acrylic and itaconic acid, acrylic acid and maleic acid and to some degree a copolymer of acrylic acid with methacrylic acid.
In the presence of water, the poly(alkenoic acid) attacks the glass powder whereby metal ions such as calcium, aluminum and strontium are released under formation of intra- and intermolecular salt bridges which crosslink the composition.
Generic cements have a number of important advantages for applications in dentistry such as the virtual absence of an exothermic reaction, no shrinkage during setting, no free monomer in the set composition, high dimensional stability, fluoride release and good adhesion to tooth structure.
Beside these advantageous properties, the main limitation of the glass ionomer cements is their relative lack of strength and low resistance to abrasion and wear. Conventional glass ionomer cements have low flexural strength but high modulus of elasticity, and are therefore very brittle and prone to bulk fracture.
In order to improve the mechanic properties especially flexural strength and fracture toughness numerous investigations were carried out in the last decades, which are directed to the use of amino acids (Z. Ouyang, S. K. Sneckberger, E. C. Kao, B. M. Culbertson, P. W. Jagodzinski, Appl. Spectros 53 (1999) 297 301; B. M. Culbertson, D. Xie, A. Thakur, J. Macromol. Sci. Pure Appl. Chem. A 36 (1999) 681 96), the application of water soluble copolymers using poly(N-vinylpyrrolidone) (D. Xie, B. M. Culbertson, G. J. Wang, J. Macromol. Sci. Pure Appl. Chem. A 35 (1998) 54761), the use of polyacids with narrow molecular weight distribution (DE 100 58 829) and star-like branched polyacids (DE 100 58 830). Further polyacids having a limited molecular mass ranging from 20,000 to 50,000 Da EP 0 797 975) and 1,000 to 50,000 Da (WO 02/41845) were proposed. A further approach was the application of spherical ionomer particles (WO 00/05182).
WO92/21632 discloses a method for treating fluoroaluminum glass with a hydrolyzable polymerizable silane.
WO2008/121895 discloses bioabsorbable elastomeric polymer networks.